A Last Will and a Trust do not cancel each other out. They govern different assets. A person who sets up a trust will transfer title of real estate and/or bank accounts to the trust and the Trustee of the trust is responsible for distributing the assets according to the terms of the trust. Asset in the trust avoid probate and court oversight. Any asset which the decedent owned individually with no other joint owner or beneficiary named on the asset is governed by the Last Will and those assets must go through the probate process. If you believe that your mother-in-law was coerced you need to consult with a probate/trust litigation attorney.